He was born in Yokohama, Japan in 1854. He emigrated to the United States around 1880. He relocated to Pasadena, California, in 1901, to the Hotel Green, where he also had a studio. He was active until 1910 and died in San Diego on April 26, 1912.
Aoki "painted portraits and murals in the homes of prominent people and became very successful." His works were handled by George T. Marsh & Company. He exhibited at the World's Columbian Exhibition in Chicago in 1893, and the Art Institute of Chicago gave him a showing in 1924.
The Fine Arts Gallery of San Francisco State University said of him: "Much of Aoki's early life in Japan is speculation, ranging from artistic pursuits (student of acting, or street artist) to the grand and spectacular (a Samurai opposed to the new Japanese government). . . . [he painted] 'spontaneous seki'e ('on the spot' or 'before the viewers' eyes'). He built a reputation as a storyteller, sketching comical figures and eventually landing an illustrating job with the San Francisco Call."
After moving to Pasadena, Aoki "worked hard to shed his reputation as an amusing character and storyteller and to be taken seriously as an artist. He began to work on 'Oriental receptions,' creating an atmosphere of a Japanese masquerade ball."
He died in San Diego in on June 26, 1912.
- Chang, Gordon; Johnson, Mark; Karlstrom, Paul; et al., eds. (2008). Asian American Art, A History, 1850–1970. Stanford, California: Stanford University Press. pp. 290–291.
- Edan Hughes, Artists in California, 1786-1940, as cited in AskArt.com
- Fine Arts Gallery, Department of Art, San Francisco State University
-  "Gossip of the Corridors," Los Angeles Herald, January 5, 1895
-  Untitled, Los Angeles Herald, January 7, 1895
-  "To See Yourselves as Aoki Sees You: Some Pictured Day Dreams of a Famous Japanese Artist," Los Angeles Herald, February 17, 1895
-  "Society's Helping Hand: Fashionable Ladies to Give an Entertainment for Kindergartens," San Francisco Call, October 25, 1896
-  "Brilliant Entertainment for Charity on 'Nob Hill,'" San Francisco Call, November 1, 1896
-  "A Bower of Beauty: Scene at Cherry Blossom Dinner: Japanese Artists' Taste for the Beautiful," Los Angeles Herald, March 9, 1903
-  Chelsea Foxwell, "Crossings and Dislocations: Toshio Aoki (1854-1912), A Japanese Artist in California, Nineteenth-Century Art Worldwide, Autumn 2012